Nonlinear optics deals with the interaction of light waves due to an electromagnetic field dependent susceptibility of an optically transparent substrate. Nonlinear optical effects are observed at light intensities which are sufficiently high that the electric field of the light waves is significant in comparison with the Coulomb electric field binding the electrons in the atoms and molecules of the light transmitting solid medium. Monochromatic light of the required intensity (e.g., 10.sup.7 V/cm) first became available with the discovery of the laser in 1960.
It is known that organic and polymeric materials with large delocalized .pi.-electron systems can exhibit nonlinear optical response, which in many cases is a much larger response than that shown by inorganic substrates.
In addition, the properties of organic and polymeric materials can be varied to optimize other desirable properties, such as mechanical and thermoxidative stability and high laser damage threshold, with preservation of the electronic interactions responsible for nonlinear optical effects.
Thin films of organic or polymeric materials with large second-order nonlinearities in combination with silicon-based electronic circuitry have potential as systems for laser modulation and deflection, information control in optical circuitry, and the like.
Other novel processes occurring through third-order nonlinearity such as degenerate four-wave mixing, whereby real-time processing of optical fields occurs, have potential utility in such diverse fields as optical communications and integrated circuit fabrication.
Of particular importance for conjugated organic systems is the fact that the origin of the nonlinear effects is the polarization of the .pi.-electron cloud as opposed to displacement or rearrangement of nuclear coordinates found in inorganic materials.
Nonlinear optical properties of organic and polymeric materials was the subject of a symposium sponsored by the ACS division of Polymer Chemistry at the 18th meeting of the American Chemical Society, September 1982. Papers presented at the meeting are published in ACS Symposium Series 233, American Chemical Society, Washington, D.C. 1983.
The above recited publications are incorporated herein by reference.
There is continuing research effort to develop new nonlinear optical organic systems for prospective novel phenomena and devices adapted for laser frequency conversion, information control in optical circuitry, light valves and optical switches. The potential utility of organic materials with large second-order and third-order nonlinearities for very high frequency application contrasts with the bandwidth limitations of conventional inorganic electrooptic materials.
Accordingly, it is an object of this invention to provide novel high performance nonlinear optical substrates.
It is another object of this invention to provide nonlinear optical organic substrates exhibiting a high .chi..sup.(2) susceptibility value.
It is another object of this invention to provide a solid phase nonlinear optical organic medium characterized by a high Miller's delta, an absence of interfering fluorescence, and a high optical damage threshold.
It is a further object of this invention to provide a nonlinear optical substrate which comprises a noncentrosymmetric configuration of aligned molecules having a diphenoquinodimethane conjugated structure.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.